TRANSITION-METAL CARBYNE COMPLEXES .102. ALKYLATION OF NA[CPMO(CO)2(CN(T)BU)] - INFLUENCE OF ISOCYANIDE SUBSTITUENTS ON REACTIVITY

Reduction of cis/trans-CpMo(CO)2(CNtBu)I (1a/1b) (Cp = eta-5-C5H5) with an excess of sodium gives the Mo0-metallate Na[CpMo(CO)2(CNtBu)] (2) in quantitative yield. Complex 2 is alkylated by Et3OBF4 at both the metal center and the isocyanide nitrogen. Reaction at the metal center leads to a mixture of the Mo(II) isomers cis- and trans-CpMo(CO)2(CNtBu)(Et) (3a, 3b), while reaction at the isocyanide nitrogen gives the aminocarbyne complex Cp(CO)2Mo=CN(Et)tBu (4). The ethyl complexes 3a and 3b rearrange in refluxing THF to give a mixture of the iminoacyl complex Cp(CO)2Mo[eta-2-C(NtBu)Et] (5) and the 1-azaallyl complex Cp(CO)2Mo[eta-3-CH(Me)-CH-NtBu] (6). A comparison of the product distribution obtained in the reaction of the metallates Na[CpMo(CO)2(CNR)] (R = Et,(t)Bu) with Et3OBF4 shows a strong effect of the isocyanide substituent R on the orientation of electrophilic attack in these compounds.